A communication system generally determines the location of a UE based on the location of a Base Station (BS). The following schemes are used to locate a UE.
According to a location determination scheme in a network supporting a Global Navigation Satellite System (GNSS) (herein, referred to as a ‘GNSS’ scheme), both a BS and a UE are equipped with Global Positioning System (GPS) receivers and the BS estimates the location of the UE using signals received from GPS satellites. In the GNSS scheme, the BS notifies the UE of a list of satellites from which signals are to be received and the UE receives satellite signals according to the satellite list. Therefore, the battery consumption of the UE is reduced and only signals received from the satellites listed in the satellite list are used for location estimation.
A UE detects the cell Identifier (ID) of a BS based on such a signal as a paging message received from the BS and identifies the BS in which it is located using the cell ID. This is called an enhanced cell ID scheme. The enhanced cell ID scheme is complementary to a conventional cell ID scheme, for the purpose of more accurately locating a UE that is in a cell having a relatively large service area. That is, the distance between the UE and the BS and the heading of the UE are estimated using measurements of the UE and the BS in addition to the cell ID of the BS in the enhanced cell ID scheme. The measurements of the UE include a Received Signal Strength Indicator (RSSI), a Reference Signal Received Power (RSRP), and a Reference Signal Received Quality (RSRQ), and the measurements of the BS include a Time of Arrival (TA) and an Angle of Arrival (AoA).
A third scheme for locating a UE is an Observed Time Difference Of Arrival (OTDOA) scheme. A UE receives Positioning Reference Signals (PRSs) from a plurality of BSs at the same point of time and estimates the distances between the UE and two or more BSs using the TDOAs of the PRSs, thereby estimating its location.
The above conventional UE location determination schemes commonly estimate the location of a UE based on the location of a BS that is serving the UE, determined by a GPS receiver equipped in the UE.
However, when a BS is connected to a plurality of Remote Radio Heads (RRHs) to extend the service area of the BS, an RRH that is providing a service to a UE cannot be identified only based on the location of the BS. Therefore, it is difficult to accurately determine the location of the UE that is within the service area of the RRH.